Coatings are sometimes used to impart desirable properties to machine components. For instance, a coating may be used to increase the cavitation resistance of a component. Cavitation is material damage caused by the formation and collapse of bubbles, in a liquid. The cavities typically arise from rapid changes in pressure due to vibrations or turbulent flow. During cavitation, the implosion of the bubbles formed in the liquid on the component surface erodes the surface. Cavitation is a source of concern in machine parts that are subject to vibratory forces while in contact with a liquid. Different materials offer different levels of resistance to cavitation. Cast iron is a material known to have relatively low resistance to cavitation. Examples of cast iron machine components that are susceptible to cavitation include, among others, housings of pumps and liners of engine cylinders.
A cylinder liner (referred to herein as a “liner”) is a removable cylindrical part fitted into an engine block of an internal combustion engine to form a cylinder. Typically, liners are made of steel or cast iron. An inside surface of the liner bounds the combustion chamber of the cylinder. During operation of the engine, the liners get heated due to the combustion of fuel in the combustion chamber. To cool the liner, a liquid coolant (such as, water) is circulated through a cooling jacket extending about a portion of the outer surface of the liner. Typically, the outer surface of the liner is in direct contact with the coolant circulating through the cooling jacket. It is known that the region of the liner in contact with the coolant experiences erosion from cavitation. Typically, the outer surface of the liner may be treated to increase its resistance to cavitation.
U.S. Pat. No. 7,617,805 (the '805 patent) discloses a method of heat treating the outer surface of the liner to provide a hardened layer of purely martensitic microstructure to inhibit cavitation induced erosion. While the hardened outer layer of the '805 patent may provide some protection from cavitation induced erosion, it may not provide sufficient cavitation protection and/or be suitable for all applications.
The present disclosure is directed to overcoming these or other limitations in existing technology.